Novolak resins in deformation imaging

ABSTRACT

IT HAS BEEN DETERMINED THAT UPON THE ADDITION AN AROMATIC COMPOUND, PREFERABLY AN ARYL AMINE COMPOUND TO A PHENOL-ALDEHYDE TYPE RESIN THAT IS NOW POSSIBLE TO FORM EXCELLENT SURFACE DEFORMATION IMAGES OF ENHANCED QUALITY ON THE SURFACE OF THE LATTER MATERIALS. THUS, UPON THE ADDITION OF THE SPECIFIED ADDITIVE TO A PHENOL-ALDEHYDE TYPE RESIN THE FROST CHARACTERISTICS THEREOF ARE SUBSTANTIALLY ENHANCED.

United States Patent 3,672,886 NOVOLAK RESINS IN DEFORMATION IMAGING Joseph Mammiuo, Penfield, N.Y., assignor to Xerox Corporation, Rochester, NY.

No Drawing. Continuation-impart of application Ser. No. 421,613, Dec. 28, 1964. This application Dec. 26, 1968, Ser. No. 787,260

Int. Cl. G03g 13/22 US. Cl. 96-1-1 5 Claims ABSTRACT OF THE DISCLOSURE BACKGROUND OF THE INVENTION This application is a continuation-in-part of copending application Ser. No. 421,613 filed Dec. 28, 1964 now abandoned, and relates to electrophotography and more specifically, to electrostatic recording on surface deformable materials.

It is known to record on deformable dielectric materials by the use of two distinct methods. The first method is known as frosting and the second method is known as relief. In frost imaging solid area coverage of the images is provided whereas in relief imaging only line copy image reproduction may be achieved. The frost process is discussed in great detail in a publication entitled A Cyclic Xerographic Method Based on Frost Deformation by R. W. Gundlach and C. I. Claus, Journal of Photographic Science and Engineering, February edition, 1963. The relief process has been described in U.S. Pats. 3,055,006, 3,063,872 and 3,113,179. The processes are quite distinct both as to the manner of execution and as to the results obtained. In relief imaging deformation occurs in response to differences in charge density of adjacent areas of a thermoplastic. Inasmuch as the response is related to differences in charge density rather than absolute charge densities the method is not suited to continuous tone reproduction but provides a means of producing line copy reproduction. Frost, on the other hand, has a continuous tone capability and with the proper input of information will produce solid area coverage.

As noted in the publication above identified, the frost method may involve the electrophotographic process whereby a latent electrostatic image is produced on a thin dielectric thermoplastic film. This film is then deformed either concurrently with or subsequent to charging, by heating, or exposure to an atmosphere of solvent vapors which produce a solid area visible image. By employing the proper sequence of charging and exposure on a plastic overcoated layer a charge pattern can be created which control selective wrinkling or frosting of the deformable layer to form the solid area image. Once the image is made visible by frosting, it may then be frozen by allowing the frosted film to harden by various methods such as by removing the sources of heat. If desirable, the frost image may be erased by reexposing the imaged ma terial to the beforesaid heat or vapor sources thus permitting the deformable layer to return to its prefrosted condition.

While many relatively thin materials will deform to form relief images, it is known that these same materials, in many instances, will not form frost images. In some cases, it may be desirable to only have edge or outline imaging as is obtained by relief. However, in many instances it is more desirable to have images of solid area coverage as is obtainable by the frost process. Furthermore, it has also been noted that some thicker surface deformable electrical insulating materials, although being both reliefable and frostable, form comparatively poor frost and relief images under the circumstances. In addition, those materials found to be suitable only for forming relief images have also, in a number of cases, been found to produce poor relief results. Because of thinness requirements, material consideraations and other required surfaced deformable properties, the selection of compositions for use in either or both frost and relief is rather restricted. Certain thermoplastic materials, for example, that may have the desirable physical properties for commercial relief processes have been found unsuitable for frost imaging. In addition, many compositions, although apparently possessing all the desirable physical and electrical properties necessary for commercial utility as deformable recording media, have demonstrated that the resulting frost or relief images in a number of instances are of poor quality and considerably less suitable than others for commercial application. By necessity, the choice of surface deformable materials for either process above disclosed has been limited to a comparatively small number.

Since the deformable thermoplastic must be softened to form either type of image and since discharge begins to take place by ion migration when the thermoplastics are softened, some thermoplastics cannot form frost images according to presently known techniques inasmuch as too much charge is lost from the surfaces of these films before they are sufiiciently softened for deformation to take place. This problem has significantly limited the choice of materials which may be employed in the frost process, eliminating many otherwise highly desirable materials as possible selections.

It is therefore an object of this invention to provide a surface deformable imaging system which will overcome the above-noted disadvantages.

It is a further object of this invention to provide a process which will allow for the use of a wider selection of surface deformable materials capable of producing images of substantially higher quality.

Another object of this invention is to provide a surface deformable imaging process utilizing a wider variety of surface deformable materials.

Still a further object of this invention is to provide a novel process for producing images of comparatively high quality on materials previously found to be unsuitable for such use.

Still another object of this invention is to provide a novel surface deformable imaging system.

Yet, still another object of this invention is to provide a novel method of frost imaging utilizing prior substantially non-frostable materials.

The foregoing objects and others are accomplished in accordance with the present invention generally speaking by providing a means of converting a substantially nonfrostable insulating thermoplastic material to a frostable material or, as the case may be, to substantially improve the image forming properties of the particular surface deformable thermoplastic recording media. By blending a phenol-aldehyde resin with an aromatic additive, particularly an arylamine compound, the phenol-aldehyde resins have now been found suitable for use in the conventional frost imaging process where heretonow they have been found generally unsuitable for use as such. The particular aromatic additive is generally used in an amount ranging from about /s part to about 2 parts of the aromatic additive per 1 part of the phenol-aldehyde resin. A

preferred range for producing the highest quality images is from about /3 part to about parts additive per 1 part resin. The additives employed are generally solid under ambient conditions (at a room temperature of about 70 F.) such that they do not bleed from the composition during storage and preferably do not have a melting point significantly higher than 185 C.

It has been determined in the course of the present in vention that upon the addition of certain aromatic additives preferably arylamine compounds to the phenol-aldehyde type resin of the novolak variety that it is now possi ble to use the phenolaldehyde resins as readily frostable materials. Heretofore, it has generally been found that with the phenol-aldehyde resins only an extremely faint image or no image at all could be formed when utilized in conjunction with the conventional frost procedure. For example, it has been found that with certain of the arylamine compounds where the particular compound has a melting point higher than that of the resin that the resulting film of the combined materials will form excellent frost images at temperatures even lower than that of the melting point of the resin itself. 7

The resins used in the present invention generally fall in the class of phenol-aldehyde type resins of the novolak variety. Any suitable phenol-aldehyde resin may be used. Typical phenols useful in making the resins herein the subject of the present invention are phenol, cresol, xylenol, alkyl phenols, such as p-tertiary butyl phenol, p-cyclohexyl phenol, aryl phenols such as p-phenyl phenol, triphenyl-phydroxy phenol, alkenyl phenols such as para, and ortho-l S-di and 1,3-di-butenyl phenol, 1,3,5 tributenyl phenol, halogenated phenols such as mono, di, tri and tetra chlorinated phenol, resorcinol, hydroquinone, and mixtures thereof; sulfonated phenols such as p-hydroxy-terbutylbenzene sulfonic acid, dihydric, trihydric, and polyhydric phenols such as resorcinol, catechol, hydroquinone, pyrocatechol, pyrogallol, phloroglucinol, benzenetriol, xylenol. polynuclear phenols such as alpha and beta naphthol, anthracene phenol, dihydroxy-di-phenyl alkanes such as bisphenol A and mixtures thereof. Any suitable substituted phenol as set out above may be used in the course of the present invention. 7

Any suitable aldehyde may be used in the reaction with the phenol. Typical aldehydes includes formaldehyde,

paraformaldehyde, furfural, amino formaldehyde, acrolein, benzaldehyde, chloral, oxo-aldehydes, acetaldehyde, glyoxal, propionaldehyde, n-butyraldehyde, isobutyraldehyde, n-valeraldehyde, isovaleraldehyde, ncaproaldehyde, n-heptaldehyde, stearaldehyde, crotonaldehydeand mixtures thereof.

The resins of this invention may be described according to the following generic structural formula, as a composition having repeating units: OH mu I R@-R Y)m z 0H Y)n /()\R-@X v 4Y)m R is a residue of a member selected from the group wherein:

consisting of formaldehyde, paraformaldehyde, furfural, amino formaldehyde, acrolein, benzaldehyde, chloral, oxo-aldehydes, acetaldehyde, glyoxal, propionaldehyde, and butyraldehyde, isobutyraldehyde, n-valeraldehyde, isovaleraldehyde, n-caproaldehyde, n-heptaldehyde, stearaldehyde, crotonaldehyde and mixtures thereof;

Y is a member selected from the group consisting of hydrogen, OH, lower alkyl (up to 6 carbon atoms), halogen and mixtures thereof;

X is a member selected from the group consisting of the above R and oxygen;

Z is an integer having a value of at least 2;

n as an integer having a value of from 1 to 4; and Y m is an integer having a value of from 1 to 3.

In general, the highly reactive phenolsform condensation products that cure rapidly to hard insoluble resins, while phenols of low reactivity form condensation products that show little or no tendency to harden. The major structural feature of a phenol that determines its reactivity with aldehydes is its functionality. This may be defined as the total number of unsubstituted positions in the benzene ring that are in ortho and para position to the hydroxyl group. An ortho-para directing group in the meta position enhances the reactivity of the phenol. Typical of the thermoplastic type resin which falls into the desirable category for purposes of the present invention are the novolak resins. For example, a typical modified phenol-formaldehyde resin of this kind is a diphenyl-oxide modified novolak resin identified as ET 395 and manufactured by the 'Dow Chemical Co. This modified novolak is the product resulting from the reaction of dimethyl-diphenyloxide with phenol under conditions which allow for the formation of a novolak structure. Typical properties for this material are:

Softening point* -L 75100 C.

*Ring and Ball method.

The softening point and molecular weight may be controlled by the ratio of phenol to dimethyl-diphenyl oxide reaction mixture.

As stated above, any suitable aromatic compound or mixtures thereof may be used as the additive in this invention. Typical aromaticcompounds include: durene; pentamethylbenzene; hexamethylbenzene; hexaethylbenzene; diphenylmethane; triphenylmethane; diphenyl; pterphenyl; 1,3,5-triphenylbenzene, naphthalene; acenaphthene; fluorene; phenanthrene; fluoranthrene; tetraphenylethylene; isoquinoline; indole; acridine; phenyl carbonate and mixtures thereof. Typical aromatic amines include: p-toluidine, 0-, m-, and p-, nitroaniline, o-, m-, and p-, phenylenediamine, p-anisidine, p-chloroaniline, pbromoaniline, 2,4,6-trichloraniline, 2,4,6-tribromoaniline, diphenylamine, triphenylamine, 2-methyltriphenylamine, 3-methyl-4'-nitrrotriphenylamine, 4 dimethlylaminotriphenylamine, o-tolidine, o-dianisidine, and mixtures thereof. A preferred class of additives, however, comprises arylamines such as triphenylamine and substituted triphenylamines. These are particularly preferred because they have a relatively high melting point and will, therefore, not bleed from the final film to which they are added, but on the other hand, produce a synergistic effect in this film. Thus, for example, Where a phenol aldehyde resin has one melting point and will form nothing more than a very weak frost image at best, even when its temperature is brought substantially above its melting point, is used in conjunction with a triphenylamine having a melting point higher than that of the resin, the film of combined materials will form an excellent frost image at a temperature even lower than that of the melting point of the resin. The reason for this synergistic effect is not, at present understood.

As stated above, the electrostatic charge pattern may I be applied to the phenol aldehyde resin by a number dispersed therethrough as a photoconductive particle in the film to make up a photoconductive film similar to the photoconductive pigment-insulating binder film, as de scribed in US. Pat. 3,121,007 to Middleton. Typical photoconductive materials include: sulfur, selenium, polyvinyl carbazole, anthracene, polyvinyl anthracene, anthraquinone, acylhydrazone derivatives such as 4-dimethylamino-benzylidenebenzylhydrazide; oxadiazole derivatives such as 2,5-bis-(p-aminophenyl-(1)), 1,3,4-oxadiazole; triazole derivatives such as- 2,5-bis-(4'-dimethylaminophenyl), 1,3,4-triazole; pyrazoline derivatives such as 1,3 diphenyl 5-(p-dimethylaminophenyl) pyrazoline; imidazolone derivatives such as 4 (p-dimethylaminophenyl)-5-phenyl-imidazolone; imidazoletione derivatives such as 4 (p-trimethylaminophenyl)-5-phenylimidazolethione, 2 (4-methoxyphenyl)-benzthiazole, 2-phenylbenzoxazole and mixtures thereof. In an alternative approach, the phenol aldehyde resin itself may be rendered photocond-uctive by complexing it with any suitable Lewis acid. Typical Lewis acids are: phenyl acetic acid, 6- methyl-cumaryl-acetic acid-(4), maleic acid, cinnamic acid, benzoic acid, 1-( 4-diethylamino benzoyD-benzene 2 carbocyclic acid, phthalic acid, tetrachloropththalic acid, .organic sulfonic acids, such as 4-toluene sulfonic acid, benzene sulfonic acid, organic phosphonic acids, such as 4-chloro-3-nitro-3-benzene phosphonic acid, 4- m'trophenol, picric acid, acetic anhydride, succinic anhydride,'maleic anhydride, phthalic anhydride, tetrachlorophthalic anhydride, chrysene-2, 3,8,9 tetracarboxylic acid anhydride, aluminumv chloride, zinc chloride, ferric chloride, stannic chloride, arsenic trichloride, stannous chloride, antimony pentachloride, boron trifluoride, boron trichloride, 1,4 benzoquinone, 2,5-dichloro-benzoquinone, 2,6-dichlorobenzoquinone, chloranil, 1,4-naphthaqnu'none, 2,3.- dichloro 1,4-naphthaquinone, anthraquinone, 2- methylanthraquinone, 1 chloroanthraquinone, phenanthrenequinone, acenaphthoquinone, pyranthrenequinone, chrysenequinone, thionaphthoquinone, anthraquinone-LS- disulfonic acid, 2 anilide-1,4-naphthoquinone sultfonic acid, triphthaloyl benzene, bromal, 4'-nitro benzaldehyde, 2,6 dichlorobenzaldehyde, 2-ethoxy-l-naphthaldehyde, anthracene-9 aldehyde, pyrene-3-aldehyde, oxinal-2w6-a1- dehyde,. pyridin-2,6-dialdehyde, biphenyl-4-aldehyde, furfural, acetophenone, benzophenone, 2 acetylnaphthalene, benzyl, benzoin, S-benzoyl acenaphthalene, biacendion, 9 benzoyl-anthracene, 4 (4-dimethyl amino cinnamoyl)-1-acetyl-benzene, anilide of acetic acid, (1,3)- indanedione, acenaphthenquinone dichloride and 2,4,7- trinitrofluorenone and mixtures thereof. These Lewis acids may also be used to sensitize the organic photoconductors listed above.

The general nature of the invention having been set forth, the following examples are given in further and more specific illustration thereof. Unless otherwise indicated, all parts in the examples are taken by weight.

EXAMPLE I One gram of a diphenyl oxide modified p-tertiary butyphenol-formaldehyde resin, available from the Dow Chemical Company under the designation NO-ET 693, having a melting point of about 110 C., is dissolved in 9 grams of toluene with stirring. To this solution, there is added one half gram of triphenylamine (melting point 126 C.), and then it is applied to a conductive substrate of aluminum and force dried at about 60 C. for of an hour. This coating is then charged negatively to about 300 volts DC in the dark with a corona discharge electrode which is scanned across its surface and heated to about 90 C. at which point a uniform, dense frost deformation pattern appears on its surface.

EXAMPLE II The procedure of Example I is repeated with the exception that gram of 2,4,7-trinitrofluorenone is added to the coating formulation and after charging of the dried film, it is exposed to a light image with an exposure of 15 foot candle seconds and then heated in the dark to a temperature of about 100 C., at which point a frost image in the pattern of the light image is seen to form on the surface of the coated film.

EXAMPLE HI The procedure of Example I is repeated with the exception that the triphenylamine is not employed in the coating formulation. Heating as high as 120C. only produces an extremely faint deformation pattern on the surface of the coated film which is poor in definition and low density.

EXAMPLE IV The procedure of Example II is repeated with the exception that the triphenylamine is eliminated from the coating formulation with the result that a very spotty image of extremely low density is produced when the film is heated to 115 C.

EXAMPLE V The procedure of Example H is repeated with the exception that one half gram of phenylcarbonate is used to replace the triphenylamine. Although the image produced is not quite so dense as the one produced in Example II, it has markedly higher density than the Example II film and the deformation pattern produced is very uniform.

EXAMPLE VI The procedure of Example I is repeated using one half gram of triphenylmethane in place of the triphenylamine. Here again, density and uniformity of the deformation pattern are much improved over that produced in Example III EXAMPLE VII One part of a p-phenylphenol-formaldehyde resin having a melting point of about C. is dissolved in 9 parts of a 50/50% mixture of toluene and methylethyl ketone with stirring. This solution is then applied to an aluminum sheet and force dried at about 60 C. for of an hour. The dried coating is then charged negatively to about 300 volts DC with a corona discharge electrode which is scanned across its surface in the dark. The coating is then heated to C. at which point an extremely faint, spotty frost deformation pattern forms on its surface.

EXAMPLE VIII To the coating solution of Example VII, there is added 0.4 part by Weight of triphenylamine (M.P. 126 C.) which is then coated on the same type of aluminum substrate as in Example VII, charged at 300 volts DC in the dark with the same corona discharge electrode and heated to about 87 C. whereupon a uniformly, dense frost deformation pattern appears on its surface.

EXAMPLE IX The procedure of Example VIII is repeated with the exception that 0.25 part of 2,4,7-trinitrofluorenone is added to the coating solution. Prior to heating, the coating is exposed to an image with a visible light source. Here again, a uniform, high density frost pattern occurs upon heating to about 87 C., but it forms only in unexposed areas of the coating.

EXAMPLE X The coating solution of Example VII is again formulated and 0.5 part of diphenylamine is added thereto prior to coating. After charging and heating to about 77 C., as described above, a uniform, frost pattern of high density is found to form across the surface of the charged coating.

EXAMPLE XI To the coating solution of Example VII, there is added 0.4 gram of o-phenylene diamine. After charging and heating, as in Example VII, it is found that a uniform high density frost image with slightly lower density than Example X is formed at about 100 C.

7 EXAMPLE XII One part of a diphenyl oxide modified phenol-formaldehyde resin having a molecular weight of about 1250 and a melting range of 96 to 115 (3., available from the Dow Chemical Company under the designation ET-395- 1300, is dissolved in 9 parts of a 50/50 toluenemethyl ethyl ketone mixture, coated on the same type of aluminum sheet as employed in Example I and force dried at about 65 C. for one half hour. Upon negative charging to about 300 volts DC in the dark with the same corona discharge technique employed in Example I and subsequent heating to 120 C., virtually no visible frost deformation pattern is formed on the surface of the coating.

EXAMPLE XIII 0.35 part by weight of diphenyl are added to a reformulation of the Example XI solution and this coating is then applied to an aluminum substrate, force dried, charged and heated in the same manner as employed in connection with Example XII. A uniform, high density frost pattern is found to occur at about 82 C.v

EXAMPLE XIV 0.5 part of triphenylamine are added to a re-formulation of the coating solution of Example XII, and this coating material is then applied to the aluminum substrate, force dried, charged and heated in the same manner as in Example XII. It is found that a uniform, very high density frost pattern forms across the whole surface of the coating at about 105 C.

EXAMPLE XV About 0.25 part of 2,4,7-trinitrofluorenone are added to a re-formulation of the coating solution of Example XIV and after force drying and charging, according to the same procedure employed in Example XIV, the coating is exposed to an image pattern with a visible light source and is then heated as in Example XIV. Here again, a high density frost deformation pattern is formed but it only appears in unexposed areas.

EXAMPLE XVI The procedure of Example XII is repeated with the exception that 0.4 part of naphthalene are added to the coating solution. This is found to result in the'production of a uniform, high density, frost pattern on the surface of the coating upon heating to about 80 C.

Although the present examples were specific in terms of conditions and materials used, any of the above listed typical materials may be substituted where suitable in the above examples with similar results being obtained. In addition to the steps used to carry out the process of the present invention, other steps or modifications may be used, if desirable. For example, the frost image formed may be fixed, erased and then refrosted at least more than one time. In addition, other materials may be incorporated in the surface deformable material and additive which will enhance, synergize, or otherwise desirably effect the properties of these materials for their present use.

Any one skilled in the art will have other modifications occur to him based on the teachings of the present invention. These modifications are intended to be encompassed Within the scope of this invention.

What is claimed is:

1. A frost imaging process comprising forming an electrostatic charge pattern on the surface of a surface deformable material which comprises a phenol-aldehyde novolak resin and an additive, said phenolaldehyde' constituent having the following generic structure with repeating units:

wherein:

R is a residue selected from at least onemember of the group consisting of formaldehyde, paraformaldehyde, furfural, aminoformaldehyde, acrolein, benzaldehyde, chloral, oxoaldehydes, acetaldehyde, glyoxal, propionaldehyde, butyraldehyde, isobutyraldehyde, N-valeraldehyde, isovaleraldehyde, n-caproaldehyde, n-heptaldehyde, stearaldehyde, and crotonaldehyde;

Y is selected from at least one member of the-group consisting of hydrogen, hydroxyl, lower alkyl'(up to 6 carbon atoms), and halogen; I

X is selected from at least one member of the group consisting of the above R and oxygen;

Z is an integer having a value of at least 2;

n is an integer having a value of from 1 to 4; and i m is an integer having a value of from 1 to 3;

said additive being selected from at least one member of the group consisting of triphenylamine,triphenylmethane, diphenylamine, 2 methyl triphenylamine, 3 methyl-4' nitro-triphenylamine, 4 dimethylamino triphenylamine, tetra-phenylethylene, naphthalene, diphenyl, o-phenylenediamine, and phenylcarbonate, said additive having a melting point of between about F. and C. and softening said surface deformable material at a temperature' lower than the melting point of saidresin to form a frost deformable pattern thereon.

2. The process as disclosed in claim 1 wherein said additive comprises triphenylamine.

3. The process as disclosed in claim '1 wherein said surface deformable material further comprises a photoconductive insulating material and said electrostatic charge pattern is formed by uniformly charging the surface of said surface deformable material and selectively exposing said charged surface to a lightimage. I

4. The process as disclosed in claim 1 wherein said ratio of resin to additive is from about 1 part by we'ight of resin to /3 part by weight of additive to about 1' part by weight of resin to about part by weight of additive. 5. The .process as disclosed in claim 1 wherein said resin comprises adiphenyl oxide modified phenol formaldehyde resin. References Cited Brynko 96--l.1

GEORGE F. LESMES, Primary Examiner J. C. COOPER III, Assistant Examiner us. 01. X.R.

34674 TP; 1786.6 TP; 340-173 TP; 96 1.s; 260 53 R 

